Logo
FULL SITE MENU

Johnson 50hp 1973

D

dlawes

New member
Just started working on a 1973 50hp johnson 50ESL73R, that I purchased last week. Started the motor and it wants to run but it is hard to start and runs rough. It seems to be starving for gas and dies out after about a minute. Been awhile since I've worked on any outboards but I am ready to get my hands dirty. Should I consider starting by rebuilding the carbs? Besides the Re-Build kit and Air Box gaskets, are there any other parts i will need. Please advise.
 
Start by doing a comp test. Max difference between cylinders 10%.
Then verify that ignition works on both cylinders.
When testing, run in a barrel and NOT on muffs to get correct back pressure.
Muffs only to flush engine, nothing else.
Check water pump and temp.
After these tests, perhaps you have quite a shopping list going through???
 
Start your work with a compression check. Expecting 100lbs or above on all cylinders. No more than 10% variation between one cylinder to another. Once you know you have a healthy motor, check the spark. It should be consistently strong that jumps a 7/16'' gap, then move to the carb cleaning, not all the time you need a kit if everything else is still intact. New spark plugs is mandatory no matter how good they look (my way of servicing an outboard), check and readjust everything, leave the carb cover out and sync the carb, check the TDC/BDC timing. Everything is good and electric choke work + fresh gas at 50:1 mix, motor will start up quickly. Advance the timing to get perfect idle while in the water, not on the muffs.
Good luck.
 
qhn said:
Hiffiman37,
:) we just posted the same reply at the same time....what a coincident!
Click to expand...
No big coincidence, just SOP for any new 'unknown' engine.
Sometimes a bit sad to see how people throws good money after bad just because they did not do a minimum of testing.
 
I would add one thing. Very close inspection of all fuel lines and fuel pump.
If compression and spark are good, and it were mine, I would replace lines and pump unless it was done recently.
 
Thanks for the quick reply. I will work on your methods today and see where I'm at. You guys are the Pro's not me. Bare with me. I am a novice but I am not afraid. Perhaps I should consider a repair manual. I love these older Johnsons. I have a 1970 20hp that I have had since I was a teenager and I have had no problems with it except a water-pump. ( Duck Hunting muck :( ). I also Have another 55hp still in my van. Plenty work to be done. But like you say, I don't want to throw good money after bad.
 
Checked compression 145 top and bottom. Spark on #2 cylinder. No spark on #1 cylinder. #1 coil looks like it has been replaced, not sure when. Should I swap coils and see if the coil is bad, or is there be something else to look for?
 
Spark jumps any gap better than no spark. Most people just bent the spark plug gap outward and ground it to the block. We mechanics on the other hand have our tools; either a timing light or a spark testing pen or home-made spark tester with a light bulb.
Anyways, "yes" you should swap the coil to see if the problem moves. If it doesn't, it's likely that your power pack is bad. You won't be able to test the power pack, but before you replace it, be sure to disconnect any killswitch if eqipped and test again. Check all ground wires (especially) to the coils and sand down if there's any electrolysis or corrosion, etc...
If the problem move, yes, it's the coil. Testing the coil is easy. Either, it's short to ground from boot to ground or no resistance between 2 terminals. Between .02 to .06 is good.
Get a manual.

Good luck.
 
Went back to swap coils and tested the spark on the #2 cylinder and found that the spark that I thought was good was iff'y at best. Can I assume that the power pack is causing the lack of spark? Still need to buy the repair manual. At this point the repair is beyond the scope of my knowledge.:( Seasons are changing fast and I guess I will have to stew about the repair over the winter. Still determined to do the repair myself. I am going to pull the 55 out of my van and see if I have any better luck. Will start a new thread if warranted. Thanks so much for the lesson in fatality.

Dave
 
Back
Top